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Dunkirk Quantum Q90 Thoughts??

Tom Hopkins
Tom Hopkins Member Posts: 552
I'm not a pro, but I looked at the Dunkirk and others and here is my thought. The Dunkirk can modulate down to about 90K BTU versus about 25K to 40K for many other Mod/Con boilers. Your 80k BTU is likely for an outside design temp of say 10 degrees or less. During spring/fall and warm winter days you need less BTU. If the boiler can not modulate down to that level, then you are just burning gas for no good reason.

I am going with a Weil-Mclain Ultra 155 and indirect DHW. It modulates down to about 33K BTU and up to about 144 BTU. Due not really need all of the high output for heat, it is more for the indirect DHW load. Might be able to go down to an Ultra 105, but have a concern that the wife could run out of hot water in the bath. I looked at others with similar heat output. The decision to go with Wm was based more on my contractors ability to install and service the boiler.



  • Chuck_20
    Chuck_20 Member Posts: 13
    Thoughts on Boiler Choices - Weil, Dunkirk,Viesmann, Buderus etc

    I have a house that requires around 80,000 btuh to heat. We are considering a new boiler and a possible option for indirect water heating. The existing boiler is/was 80% and installed in 1984.

    I'd like to get input on the reliability of a Dunkirk Quantum Hi-Efficiency boiler vs others on the market.

    I've been quoted boiler changeouts ranging from $4,200 - $10,000 both foreign and domestic with and without indirect water heating.

    There's so many different Residential boilers and options any help would be appreciated

  • mitchb
    mitchb Member Posts: 19
    the Q90

    is not a modulating boiler. The 90 series is fixed input. Have installed a buch. no trouble, good quiet boiler.

    Depending on your system it could be a great fit. If you have a single loop / zone baseboard, I would use the fix Q90-100, and an outdoor reset and modulate the water temp.
    Modulating makes great sense in a multi zone system where the load demand varies as the different zones open and close.

    Not to say that modcons would not work in a single loop, they will. But you can save more with them in multi zone systems.

    By using the fixed input unit and an outdoor reset, you can modulate the water temp, keeping the boiler in its condensing zone as pften as possible, without expensive exotic modulating burner controls.

    THe Q90 uses a simple inducer, 24v gas valve / HSI system that is really easy to test, and replce / repair should it break down.

    My 2 cents
  • Empire_2
    Empire_2 Member Posts: 2,343
    additional thoughts

    The Q90 is a nice boiler and it can be pipped directly to any and all circuits. The Weil McLain Ultra has to be pipped primary Secondary. Now the Q95 is a full mod/Con boiler......

    Miike T.
  • Wayco Wayne_2
    Wayco Wayne_2 Member Posts: 2,479
    I have one

    out there 5 years now or more. Had trouble the first year with the pressure switch failing intermittantly at high temps near 180. After 1 or 2 seconds it would start the cycle up again. Short diagnostic opportunity, and I was wearing out ceramic ignitors from the cycling. Since it had no diagnostics at the time I had no idea what was happening and would wait for long periods of time hoping to have my meter in the right place and my focus sharp for when it happened. I Finally got the right tech support person and the pressure switch needed adjusting. No problems since. Thank God the HO was a patient person. It took a while to solve. I hope they have a better set up now. WW

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  • Al Corelli_2
    Al Corelli_2 Member Posts: 395
    I like it so much...

    I have one in my house. Serial number 004.

    With outdoor reset, it stays in condensing mode for most of the season.

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    Al Corelli, NY

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